Method for carrying out a gear shifting operation in automated transmissions

#This application is a National Stage completion of PCT/EP2011/055090 filed Apr. 1, 2011, which claims priority from German patent application serial no. 10 2010 028 670.2 filed May 6, 2010.

#The present invention relates to a method for performing a shift operation in an automatic transmission with an automated, at least form-locking shift transmission.

#From automotive technology, it is known with automatic transmissions in which at least one transmission part is designed as a so-called constant mesh transmission that during a gear shift operation a synchronization procedure is produced using an actuator. If the vehicle is located on a significant incline or has a high rolling resistance, for instance during off-road use, the vehicle can come to a standstill or even roll backwards during a shift, due to the interruption of tractive force. In such situations it is necessary to slow down the transmission input during the synchronization procedure, and to subsequently accelerate the transmission corresponding to the vehicle speed and the drive train transmission ratio, counter to the direction of rotation of the internal combustion engine. For example, it is known from the document DE 10 2007 007 257 A1 that an electric machine is used to be able to perform the synchronization procedure despite such difficult shifting procedures in the shift transmission. However, an electric machine is essential for this purpose, such that these measures cannot be applied in transmissions without the electric machine. In addition, the use of the electric machine increases the consumption disadvantageously.

#The present invention is described in more detail using the drawing. The sole FIGURE of the invention shows a representation with different graphs in which the gear progression, the vehicle speed progression, the rotational speed progressions, and the actuation progression of the actuators are shown over time, for performing the synchronization procedure. The progressions for a downshift during which the vehicle starts to recover, are shown as an example. The proposed method can however also be used with an upshift.

#In the upper graph of the FIGURE, the presently engaged gear can be seen in that an actual gear progression GIST is indicated with a dotted line, and a target gear GZIEL progression is indicated with a solid line. From the two progressions it can be seen that at time t1, the transmission is shifted into neutral and only at time t3, after the completion of the synchronization, is the target gear shifted.

#It can be seen from the progressions of the vehicle speed VKFZ and the progression of the actual rotational speed nIST and the target rotational speed nZIEL at the transmission input in the center diagram that a reversal of the vehicle direction occurs during the shift procedure. This is also indicated by the progression of the rotational speed.

#The lower graph in the FIGURE shows the activities of the transmission brake at time t1 and at time t2, in order to reduce the transmission input rotational speed to the value of zero. From the time t2 until the time t3, the claw shifting element is activated for equalizing the remaining rotational speed difference, in order to, at time t3, engage the target gear for the completion of the shift procedure.